1. Field of the Invention
The invention relates to optical instruments, and more particularly to instruments which aid viewing.
2. Description of Related Art
It is known that under many circumstances viewing may be enhanced by instruments which restrict the field of view. Among U.S. Patents which seek to improve viewing in this way, the following are representative:
U.S. Pat. No. 854,546 to Verdeau, May 21, 1907, for "EYE PROTECTOR" shows a mask with light restrictive horizontal eye slots 7.
U.S. Pat. No. 1,067,793 to Barr, July 22, 1913, for "AUTOMOBILE GOGGLES" shows a pair of eye shields each having a horizontal cut out slot 8.
U.S. Pat. No. 1,712,360 to Slaughter, May 7, 1929 for "SPECTACLES" shows an element 8 which has a longitudinal horizontal slot 14 registering with a slot 10 and element 22 have a longitudinal slot 24 which registers with slot 10 and opening 14. Finally a peep hole 18 further restricts the field of view.
U.S. Pat. No. 1,954,184 to Schlumbohm, Apr. 10, 1934, for "OPTICAL DEVICE" shows a short tube 2 projecting from a glass plate 7. The tube 10 has a horizontal slot or opening 2 to restrict light input to the eye.
U.S. Pat. No. 1,982,650 to Fletcher, Dec. 4, 1934, for "OPTICAL DEVICE" shows rims of a pair of glasses each provided with a diaphragm 12 having a horizontal slot and a forward projecting tube in registry with the slot.
U.S. Pat. No. 1,983,312 to Schlumbohm, Dec. 4, 1934, for "OPTICAL DEVICE" is similar to the above mentioned Schlumbohm U.S. Pat. No. 1,954,184 in restricting by a tube with a horizontal slot light entering the eye.
These patents seek to control the entry of undesired light to the eye either by using a horizontal slit, which affords no adjustment to ambient light conditions, or a peep hole which greatly restricts the field of view and also may greatly restrict the amount of light. The use of electronics requires a power supply and esoteric materials.